1. FIELD OF THE INVENTION
The present invention relates generally to a ball screw integrated type linear movement guiding unit preferably employable for, e.g., an actuating arm of a robot, a X-Y coordinate table or the like. More particularly, the present invention relates to a ball screw integrated type linear movement guiding unit which assures operation at a high speed, position determination with high accuracy and reduction of the number of components required for constructing the guiding unit.
2. DESCRIPTION OF THE PRIOR ART
A typical conventional ball screw integrated type linear movement guiding unit is disclosed in a Japanese Utility Model Laid-Open Publication No. Hei. 2-12554.
This conventional guiding unit includes a male-threaded screw shaft having a spirally extending ball screw groove formed around the outer surface thereof and a guide rail of which opposite side walls have an axially extending ball rolling groove formed on the inside wall surface, respectively, while the screw shaft is interposed between both the side walls of the guide rail. A nut is threadably engaged with the screw shaft via a number oddballs rolling through the ball screw groove. In addition, ball rolling grooves are formed on the opposite surfaces of the nut corresponding to the ball rolling grooves on both the side walls of the guide rail so that the nut linearly axially moves in the forward/rearward direction via a number of balls rolling through the aforementioned ball rolling grooves.
With the conventional guiding unit constructed in the above-described manner, however, since a ball recirculating section in a ball screw system for recirculating balls through the ball screw groove on the screw shaft and the ball screw groove in the nut is constructed in a so-called U-shaped ball recirculating tube type so as to allow it to be fitted to the upper part of the nut, it is practically difficult that the screw shaft is designed to have a long lead. Thus, there arises a problem that it is difficult to satisfy requests raised from users for operation at a higher speed and position determination, with higher accuracy.
On the other hand, a ball recirculating section in a linear movement guiding system for recirculating balls through the ball rolling grooves on the guide rail and the nut is designed in the form of an U-shaped curved passage to be individually attached to the opposite end surface of the nut. Thus, there arises another problem that the number of components required for constructing the guiding unit is unavoidably increased, and moreover, an assembling operation is performed only with many manhours.